Thin Air Might Increase Depression in Mountain States

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The eight intermountain states of the American West, sometimes
called the Suicide Belt, have high elevations and the associated
thin air. Now, researchers say the low oxygen in these areas is
linked with signs of depression, and could potentially even
contribute to suicides in some regions.

In 2012, Colorado, Wyoming, Utah, Montana, Idaho, Nevada, Arizona
and New Mexico all had suicide rates exceeding 18 per 100,000
people, while the national rate was 12.5 per 100,000 people,
according to the American Foundation for Suicide Prevention.

These states tend toward higher elevations, and several studies
have identified living at higher elevations as an independent
risk factor for suicide. Other studies have also found that
rates of depression increase with elevation and may
contribute to increased suicide risk.

In the new study, researchers at the University of Utah and one
colleague at Tufts University found that female rats exposed to
high-elevation conditions — both simulated and real — exhibited
increased depressionlike behavior. The behavior could have been
due to the animals experiencing hypoxia, a condition in which an
individual gets insufficient oxygen, the researchers said.
[ 5
Myths About Suicide, Debunked ]

Male rats showed no increased signs of depression when exposed to
the same levels of hypoxia, the researchers found. Female
mammals, including humans and rats, naturally produce less of the
brain chemical serotonin than males. The neurotransmitter is
thought to contribute to feelings of well-being and happiness,
and as such, the higher levels in males may make them less
susceptible to depression, researchers say.

"The significance of this animal study is that it can isolate
hypoxia as a distinct risk factor for depression in those living
at altitude," said Shami Kanekar, a research assistant and
professor of psychiatry at the
University of Utah, and a lead author on the study. It also
suggests an increased risk of depression for people who have
conditions such as chronic obstructive pulmonary disease (COPD)
or asthma, which may reduce their ability to take in oxygen, she
said.

In the experiments, the rats were kept for a week in Salt Lake
City, which has an elevation of 4,500 feet (1,370 meters), and
then in a lab under conditions that simulated the oxygen levels
at sea level, then the oxygen levels at 10,000 feet (3,050 m) and
20,000 feet (6,100 m). The researchers used a widely accepted
behavioral test in which depression in rats is gauged by the
persistence exhibited by the rodents in a swim test.

The findings bolster the argument that physiological changes
triggered by the low oxygen at higher altitude can contribute to
depression.

"There are many potential risk
factors that contribute to depression and suicide at
altitude, and we are not discounting any of these other factors
at all," said Dr. Perry F. Renshaw, a professor of psychiatry at
the University of Utah and a lead author of the study. "Several
such factors that are prevalent in the intermountain West include
poverty, rural residence, low population density, gun ownership
and psychiatric disorders such as bipolar disease."

But the new study shows that one factor inherent to
living at higher elevations — low oxygen levels — can cause
depression, Renshaw told Live Science.

Renshaw noted that the study had limitations. For example, the
brains of humans and rats are very different, particularly in the
frontal lobe, which is thought to be involved in decision making
and impulse control, among many other functions.

Renshaw said he suspects depression in thin-air locations might
be partly caused by low levels of serotonin. Hypoxia impairs an
enzyme involved in producing serotonin, which could lead to
depression, Renshaw said.

The possible link could be particularly important for women
living in higher elevations, Renshaw said.

The big question, Renshaw said, is "should we be treating women
who are depressed, and particularly those in the Rocky Mountain
states, differently?"

Renshaw's team is examining the effectiveness of antidepressants,
especially drugs called SSRIs (selective serotonin reuptake
inhibitors), which are the most commonly
prescribed antidepressants in the United States. Studies
using animals have suggested that SSRIs such as Prozac may not
work when brain serotonin levels are low.

Utah has the highest use of antidepressants in the country and
the highest rate of depression, according to a 2007 study
conducted on behalf of the nonprofit organization Mental Health
America, Renshaw said.

"The fact that both depression and suicide rates increase with
altitude implies that current antidepressant treatments are not
adequate for those suffering from depression at altitude, leading
to high levels of unresolved depression that can contribute to
higher levels of suicidal ideation and suicide attempts," Kanekar
said.

Recently, Renshaw said his team began a new study that seeks to
increase serotonin levels in women diagnosed with depression to
the levels found in women at sea level, to see if this change
could help antidepressants to work more effectively.

The number for the National Suicide Prevention Lifeline is
800-273-8255.